With at least 2.6 billion global smartphone subscriptions today and 6.1 billion global smartphone subscriptions expected by 2020, more people are using and, in some cases, relying on smartphones for access to online services and information. Approximately two-thirds of U.S. adults now own a smartphone, and almost half of U.S. adults own a tablet computer. Computer programs designed to run on a mobile device (mobile apps) provide functions which do not include running the mobile device itself. Mobile apps are designed to run on specific mobile devices, and are written for specific operating systems (e.g., iOS, Windows®, or Android™). The marketplace for mobile apps is booming with thousands of new mobile apps being introduced and millions of mobile apps being downloaded every day from digital distribution platforms called app stores (e.g., Apple® App Store, Google Play™ store, Windows Phone® Store, Amazon® Appstore, and BlackBerry® World® storefront). Mobile apps now provide users with functions including games, multimedia, communication, productivity, information retrieval, and payment services.